Shock absorber



FIG. 1 is a perspective view of a shock absorber showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof; and

FIG. 5 is a side elevation view thereof. 

The ornamental design for a shock absorber, as shown and described. 